Method and machine for blanking ball bearings



Sept. 16, 1969 L. o. CARLSEN 3,465,910

METHOD AND MACHINE FOR BLANKING BALL BEARINGS Filed June 21, 1967 8 Sheets-Sheet 1 INVENTOR.

LEONARD O. CARLSEN BY BY RUTH ROGE CARLSEN,

E CUTRIX Sept. 16, 1969 o. CARLSEN 3,466,910

METHOD AND MACHINE FOR BLANKING BALL BEARINGS Filed June 21, 1967 8 Sheets-Sheet 2 mvsmon. LEONARD o. CARLSEN av RUTH ROGERS LSEN,

BY EXE RIX A RNEY Sept. 16, 1969 L. o. CARLSEN METHOD AND MACHINE FOR BLANKING BALL BEARINGS Filed June 21. 1967 8 Sheets-Sheet INVENTOR. LEONARD 0. CARLSEN av FIG. 10

RUTH ROGERS CARLSEN,

EXECUTRIX p 16, 1969 1.. o. CARLSEN 3,466,910

METHOD AND MACHINE FOR BLANKING BALL BEARINGS Filed June 21, 1967 8 Sheets-Sheet 4 FIG. 12

INVENTOR. LEONARD O. CARLSEN BY RUTH ROGERS CARLSEN,

EXECUTRIX Sept. 6, 1969 L. o. CARLSEN 3,466,910

METHOD AND MACHINE FOR BLANKING BALL BEARINGS Filed June 21, 1967 8 Sheets-Sheet 5 JNVENTOR. LEONARD O. CARLSEN BY BY RUTH ROGERS CARLSEN,

EXECUTRIX p 16, 1969 L. o. CARLSEN 3,466,910

METHOD AND MACHINE FOR BLANKING BALL BEARINGS Filed June 21, 1967 8 Sheets-Sheet 6 INVENTOR. LEONARD o. CARLSEN BY RUTH ROGERS CARLSEN,

Y EXECUTRIX 8 Sheets-Sheet 7 09 NW: 3 n

L. O. CARLSEN Sept. 16, 1969 METHOD AND MACHINE FOR BLANKING BALL BEARINGS Filed June 21, 1967 INVENTOR. LEONARD o. CARLSEN av RUTH ROGERS CARLSEN, BY EXECUTRIX ATTOjNEY Sept; 16, 1959 1.. o. CARLSEN 3,466,910

METHOD AND MACHINE FOR BLANKING BALL BEARINGS Filed June 21, 1967 8 Sheets-Sheet a INVENTOR. LEONARD O. CARLSEN BY BY RUTH ROGERS CARLSEN,

% EXECUTRIX AITZRNEY United States Patent 3,466,910 METHOD AND MACHINE FOR BLANKING BALL BEARINGS Leonard O. Carlsen, deceased, late of Deerfield Beach,

Fla., by Ruth Rogers Carlsen, administratrix, Deerfield Beach, Fla. 33441 Filed June 21, 1967, Ser. No. 647,882

Int. Cl. B21k 1/02 US. CI. 7271 20 Claims ABSTRACT OF THE DISCLOSURE Ball bearings are blanked by feeding wire between two rollers, each having a helical groove of arcuate profile, shaped to roll out one-half of a ball. The rollers are disposed at opposite sides of the wire and rotate in engagement with and revolve about the wire. The lead of the thread of the rollers produces axial feed of the wire. Radial feed is built into the rollers; they have thread convolutions of progressively varying height and top width. The threads may cut the finished balls from the wire; or a separate cut-off tool may be employed for this purpose.

The present invention relates to the manufacture of ball blanks to be used in making balls for lubricated ball bearings.

Heretofore steel balls have been manufactured for such bearings by upsetting slugs of rod or wire between hemispherical dies. In the upsetter, wire is fed from a drum into the machine, where a single shearing stroke of a cutoff tool cuts off a slug from the wire. This slug is placed between two dies which then form the ball. With this method, the two areas (poles) corresponding to the ends of the slugs receive less working, which results in concentration of perpendicular fibers, or end grains, at these areas. Also, at the equator of the ball, which is at the die parting line, the ball has perpendicular fibers because the flashing has to be removed.

There are ample test data showing that the majority of ball failures occur in the areas having end grain (perpendicular fiber). This, then, is a disadvantage of the upsetting process.

Furthermore, this previously known process involves drastic impact which causes pitting of the dies and eventual crumbling of the edges of the holes for the pins used to knock the blank out of the die. Consequently, if the dies are used too long, there will be damage to the die contour which will result in blanks that are not complete in the equator area. This in turn will lead to a lot of scrap. Moreover, there is an excessive amount of stock wasted with the upsetting rocess. There is the stock left beyond the finished diameter plus the material in the flashing and in the knock-out holes.

In previous processes of making ball blanks, the blank, after ball-formation, is put through a rough grinding operation which involves passing a surface grinding wheel over the ball blanks, which are held in a series of grooves, to produce acceptably round blanks.

With the present process, both upsetting and rough grinding operations are eliminated.

One object of this invention is to provide a ball blank having improved grain flow, thus leading to improved bearing life.

Another object of the invention is to provide a process for producing a rounder and truer sphere, thus making possible a truer finished ball.

Another object of the invention is to provide a process for producing ball blanks which will result in a substantial reduction in the amount of material required to blank 21 ball by producing blanks closer to the desired finished Patented Sept. 16, 1969 size and shape, thereby reducing the number of grinding and lapping operations required.

A still further object of the invention is to provide a relatively simple and inexpensive machine for producing ball blanks, which will have an increased production rate as compared with the existing equipment.

In the process of the present invention, rolling dies, somewhat similar in appearance to worms of varying lead and of progressively varying profile shape, are employed. The dies are not fed toward one another, but are simply rotated in engagement with the wire or rod, from which the ball blanks are to be rolled, while relative rotation is elfected between the wire rod itself and the dies in time with the rotation of the dies. At the leading end of the dies, the ball blanks are rolled free from the wire or rod.

The wire is fed into the machine from a large drum; therefore, the wire cannot be rotated; it is held against rotation. The two dies are housed in a drum which rotates about the wire while the two dies rotate about their respective axes within the drum.

Special guides are provided to support and control the work especially during the operation of rolling off the balls.

In the drawings:

FIGS. 1 and 2 illustrate diagrammatically two alternate die designs which will roll balls;

FIGS. 3 to 8 inclusive illustrate successive steps in the rolling of balls with 9, herein preferred form of rolling tools;

FIGS. 9 and 10 are diagrammatic views illustrating the action between the thread rollers and the wire or rod during ball formation;

FIG. 11 is a diagrammatic view illustrating a further embodiment of the invention;

FIG. 12 is a fragmentary longitudinal/vertical sectional view through a machine built according to one embodiment of this invention, to roll balls from a wire or rod;

FIG. 13 is a diagrammatic view, taken on the line 1313 of FIG. 12, looking in the direction of the arrows, showing the drives to the rollers and to the drum of this machine;

FIG. 14 is a diagrammatic sectional view taken on the line 14-14 of FIG. 12;

FIG. 15 is a fragmentary view similar to FIG. 13 on a somewhat enlarged scale showing further details of the drive and showing, also, details of the mechanism for operating the end guide;

FIG. 16 is a fragmentary transverse sectional view taken at right angles to the view of FIG. 15 and on a still further enlarged scale;

FIG. 17 is a side view showing details of the mechanism for holding the wire against twisting; and

FIG. 18 is a section taken on the line 18-18 of FIG. 17 looking in the direction of the arrows.

Referring now to the drawings by numerals of reference, in FIG. 1, 30 denotes the wire or rod from which the balls are to be formed; and 31 designates one of the dies to be used in forming the ball blanks. This die is disposed at one side of the axis 32 of the wire or rod. A similar die (not shown) is disposed at the opposite side of the axis. The wire or rod size may be equal to the diameter of the ball blank 35, which is to be rolled, or be different therefrom. The die grooves are arranged on a helix.

In FIG. 1, the wire or rod diameter is approximately equal to the diameter of the balls which are to be formed. The die 31 has teeth or lands 36 of progressively increasing width whose tops extend parallel to the axis of the die and are spaced at progressively greater radial distances therefrom. The grooves or interdental spaces 37 between successive lands are of arcuate profile shape and of progressively increasing depth from one end to the other. With dies of this sort, shank portions 38 are rolled in 3 the rod between successive ball portions 35, 35", 35 35 and 35, the shank portions being rolled to a progressively reduced diameter while the ball portions are formed.

FIG. 2 shows a form of die 41 for forming from the wire or rod 40 a ball 45 which is of larger diameter than the diameter of the rod or wire 40. Again the tops of the lands 46 in the die are straight and parallel to the axis of the die and of progressively decreasing width from one end to the other whereas the interdental grooves 47 are of progressively increasing depth.

In FIG. 2, the wire has about 70% of the ball blank diameter so that as the metal is squeezed out of the necks into the center of the balls, and up the sides of the die grooves, to fill the shape, at satisfactory grain flow, in depth, will be achieved. With this method the grain flow through most of the center portion of the balls will be longitudinal while the surface grain fiow will follow the spherical shape. This is the preferred die configuration. Here the die grooves have a uniform pitch and lead making this die relatively simple to manufacture. There is gradual formation of the balls at 45' 45" 45 45 and 45. Because of the extremely high pressure angles (curved side profile shape) of the lands there will be no fold of the grain structure.

The major work (force) is applied at the necks 48, 48", 48 and 48 The lands and the sides of the grooves at their junctures must be rounded off so as to cause flow of metal. A sharp corner would tend to shear.

By providing the die with double lead grooves, for each rotation of the dies, two balls may be produced.

FIG. 3 shows a pair of dies 51, 51 having grooves of varying lead where the wire again has the same diameter as the balls to be rolled. In this case, however, the thread of the die is made of progressively decreasing width until at the point 58 it approaches a knife edge.

FIGS. 3 to 9 inclusive illustrates progressive steps in rolling ofl the necks between balls. FIG. 3 shows the lead ball 55 being rolled free from the wire rod 60. The edges of the die grooves 57 at opposite sides of the final thread convolution of each roller have been shaped to squeeze the neck stock at 58 free from the ball 55. The neck stock is rolled into an arrow-shaped configuration.

An end guide member 59 is provided to center and hold the ball during the final rolling off of the neck. Like the ball, the end guide centering member 59 does not rotate. It may be controlled by a cam mechanism which causes it to move in the same direction and at the same speed as the workpiece. The contact between the two is under a slight preload.

In FIG. 3, the neck 58 has been separated from the lead ball 55; the guide 59 is in its extreme left position, and is about to speed up to move rapidly away from the work to permit the next partially-formed ball 55" to be brought into position.

FIG. 4 shows the end guide member withdrawn, the now completed ball blank 55 falling away. As the end guide is withdrawn, the fixed stripper pin 61, which is reciprocable in the bore 62 of the end guide 59, is exposed, and operates to strip the ball blank from the concave recess 63 in the end guide. The nOW completed ball blank 55 rolls down the incline 64 out of the machine.

FIG. shows the next step where the neck 58 is being rolled free from the next ball 55". The beveled rolling edge 65 on the die 51 has a slightly larger diameter than the corresponding edge 66 on the die 51'. In this way, the edge 65 on the die 51 overlaps the end of the ball, insuring the cut-off with the two edges 65, 66 making contact, as shown in FIG. 6.

FIG. 6 shows the neck rolled free and about to roll down the incline 64 out of the machine. At the same time, the end guide members 59 has started to advance again to contact the next ball 55".

The next steps of fully advancing the end guide and I of reversing its direction, are not illustrated, but the action is cam-controlled.

FIG. 7 shows the guide and the lead ball 55" traveling in the same direction and about to make contact.

FIG. 8 shows that contact has been made and the edges of the die grooves are about to roll off the neck 58.

The cycle then begins anew in the position shown in FIG. 3.

The end guide 59 not only centers the ball, but permits the neck to be completely removed from the ball. Without the end guide, the neck would not be completely removed, since the act of rolling off the neck would force the ball forward putting a pointed end in the polar area of the ball.

To keep the work centrally located between the two dies, the die 51 has a radius, of say .0015", greater than the die 51'. This is equal to half the feed per revolution about the work.

In rolling balls, a condition similar to the condition of engagement between mating gears is established. An average pitch diameter for the ball is determined which equals the pitch diameter of the dies. The ratio between the pitch diameter of the ball and the dies determines the gearing between the drum and the dies.

The pitch diameter of the ball is denoted at 70 in FIG. 9 and the pitch radius of the die at 71. 72 is the axis of the die, and 74 is its rolling edge. On the pitch diameters, the distance A-B on the ball has exactly the same length as the distance A-C on the die. This corresponds to the work being done at 48' (FIG. 2). At this point, it is true rolling without any rotational force being exerted on the work. The surface 75 of the work, which is in engagement with the rolling edge of the die, that is, the place where the work is being done, crosses the diametral line 77 at the point Y. The line P-C crosses the rolling edge of the die at the point Z. Note that the linear distance X-Y is much longer than the distance XZ. Since the work and the die are geared together, the point Z must keep up with the point Y. This can only be done by a sliding action between the two parts. This sliding action introduces a sliding force on the work in a counterclockwise direction. Since the force from rolling is in a clockwise direction, the one force tends to balance the other, which is a favorable condition as it tends to eliminate twist or torque on the wire.

FIG. 10 shows the rolling at 48 in FIG. 2 which is well inside the pitch diameter. As in FIG. 9, the linear distance A-B is the same length as A-C. The line O-B crosses the surface being worked at M; and the line P-C extended crosses the rolling edge of the die at N. Note that the linear distance LN is greater than the distance L-M which is made up by sliding, which produces a force in a clockwise direction which is the same direction as the rolling force. However, since these combined forces are on a very small radius, they will produce very little twisting action on the wire (work).

In the known method of blanking, using the upsetting method between two dies, the action is so violent that sufficient heat is generated from slug to ball blank to cause the balls to heat to approximately 400 F.

In the case of the rolling dies of this invention, there is no shock involved, and action of rolling the balls from the wire is extended over a large surface area, constantly subject to coolant. As a result, the balls can be expected to come out of the machine in a nearly cold state. The two rolling dies have a working area approximately twice that of hemispherical dies; while less than half of the working area of the hemispherical dies is subjected to heavy working.

Based upon these differences, the rolling dies should last twenty to thirty times as long as conventional hemispherical dies. Moreover, the rolling dies can be reground ten to fifteen times before being worn out.

FIG. 11 shows two dies 100, 101 double lead, producing two balls per revolution of the dies. They act like screws to produce the feed motion of the wire 102. In this embodiment of the invention, the necks 104 between finished balls are not rolled off as in the embodiment shown in FIG. 2. Instead, a connected series of balls 105 are fed through a close fitting stationary sleeve 106 to the outside of the machine. An opening at this point permits two cut-offs tools 107 to snip off the neck of a ball. The tools then move out of the sleeve to permit the next ball to advance, etc. A collar 108 holds the lead ball during the cut-01f operation.

The cut-off tools are mounted on a slide which, at the time of cut-off, is traveling at the same rate of speed as the string of balls. The cut-off tools then retract from one another to permit the next ball to advance. The two cams control the action of the slide and the tools.

The balls 105, cut off in this manner, will have a small fiat at the polar area, and so will not have the complete roundness of the balls where the necks have been rolled 011 as illustrated in FIG. 2. They will, however, be usable, and have advantages over ball blanks produced by previous methods.

FIGS. 12 to 17 are more or less diagrammatic views illustrating the structure and operation of a machine for performing the present invention. Here the dies are designated 110 and 111. They are rotatably journaled in a rotary drum 112 which is journaled at one end on antifriction bearing 114 in the machine frame 113, and is driven from the motor 115 (FIG. 13) through pulleys 116 and 117 and a connecting belt 118, a jack shaft 120, the pulleys 121 and 123, and the belt 124. The jack shaft is journaled in the frame 113 of the machine. The pulley 123 is keyed to the drum. An idler pulley 125 on a shaft 126, that is carried by a block 127, which is slidably adjustable on a bracket 128 carried by frame 113, serves to take up belt 124. Block 127 is adjustable by rotation of screw 129 (FIG. 13), that is secured at its inner end to the slide and threads through nut 130.

The die spindles are driven from the shaft 120 through the pulleys 131, 132, belt 133 (FIG. 12), the sleeve 136, to one end of which the pulley 132 is secured, the gear 135, which is secured to the other end of the sleeve 136, pinions 137 and 137 (FIG. 14) which mesh with the gear and with the gears 138, 138, which are secured to the two die spindles 139, 139, respectively. Sleeve 136 is journaled adjacent one end on an anti-friction bearing and adjacent its other end on antifriction bearings 147. The work is shown at W being rolled between the two dies 110, 111. An idler pulley 140 (FIG. 15 secured to a shaft 141, Which is journaled in a block 142 that is slidably adjustable on a bracket 143, serves to take up belt 133. Block 142 is adjustable, like block 127, by a screw 144, like screw 129, which threads through a nut 144, and is secured at its inner end to block 142.

The end guide 59 for the work is moved to and from operative position by the cam (FIG. 15) which is driven from the sleeve 136 through the pulley 151 (FIG. 12), the belt 152, the pulley 153 (FIGS. 13 and 15), the shaft 154, to which the pulley 153 is secured, the worm 156 on the shaft 154, and a wormwheel 157 which is keyed to the shaft to which the cam 150 is fastened. A roller follower 158 (FIGS. 16 and 15), which is carried by one arm of a bellcrank lever 160 engages in the cam slot 159. Bellcrank lever 160 is pivoted at 162 on the frame of the machine and is pivotally connected at 164 to one end of a connecting rod 165.

The other end of the connecting rod is connected by a pin 166 and slot 167 with a lever 168 (FIG. 12) that is pivotally mounted tat 169 on the frame of the machine. Lever 168 is connected at its upper end by a fork 170 and pins 172 with the yoke portion 174 of a reciprocable sleeve 175 which carries at its inner end the end guide 59. The stripper rod 61 is mounted in the end guide and sleeve 175. Sleeve 175 extends into the bore of a bearing member 176, which forms part of the drum 112. The bearing member is journaled on anti-friction bearings 177 in the frame of the machine. It carries the brackets 179,

6 179' in which are journaled the shafts which carry the discs 110 and 111 and the gears 138, 138'. The brackets 179, 179' are bolted or otherwise secured to the main part of the drum 112 by studs 230 (FIG. 12).

The wire 60 from which the balls are to be rolled is fed into and through the bore of a stationary wire holder 134 (FIG. 12). To prevent twist of the wire a rolling chuck 195 may be employed on the container 134. FIGS. 17 and 18 illustrate this chuck. It consists of two rollers 180 and 181, each having two sharp peripheral edges 182. These rollers are adjusted together so that the sharp edges can slightly imbed themselves in the wire and so act as keys to prevent twist. The two rollers are mounted on anti-friction bearings 183 capable of taking a heavy load without causing any drag on the feed of the wire through the rolling die.

The sharp edge of the rollers should imbed themselves into the wire from .001" to .002, for which purpose the lower roller 181 is mounted on an eccentric pin 184, whose axis 186 is offset from the axis 187 of the associated roller. One end 189 of this pin has a plurality of angularly-spaced inclined slots 188. The pin is adjusted to make the desired indentation and locked in this position by an eccentric lock 190 having a single key 192. The angle of inclination of the slot serves to lock the eccentric pin. A screw 191 serves to hold the key member 190 in engagement with the slot 188 with which it has been engaged.

The bar 193, which carries the rolling chuck, has on its inner end an end cap 194, which serves, together with an oil seal, to prevent oil escape from the gear chamber. The rollers and the end cap can be changed to accommodate different size wire, which may vary in diameter, for instance, to produce balls from /s" to in diameter. This bar 193 also serves to bring lubricating oil to the die driving gears, through the duct 185. These gears do not rotate fast, though the drum housing them does. Accordingly, this oil will be in the form of a mist.

The wire holder 134 is centered at one end on antifriction bearings 200 and at its other end on needle bearings 201. This holder is stationary. At its outer end a plate 196 is attached to it, which together with a ring 197, is slotted to form a bayonnet type lock. To remove the holder 134 from the machine, the nuts 203 (FIG. 12) are loosened and the ring 197 is turned to a stop (not shown) by a knob 198. Two knobs 198 may be provided to make it easy to turn the plate. Two knobs 199 can be used to pull the holder 134 and its chuck free of the machine. This, however, does not remove the wire, which is locked in the dies.

To remove the wire the hand crank 205 is moved to engage the jack shaft 120 through the square tooth clutch teeth 207 (FIG. 12). This movement is made by turning the thumbscrew 208 to unscrew it from a hole in the bracket 211 and turning the lever 212 to a new position. The lever 212 is held to an eccentric pin 209. The offset eccentric portion of the pin 209 engages a slot in the shaft 214 which holds the crank 205. A limit switch 210 engages a shoulder on the shaft 209 which has a dip in it to permit the engagement of the clutch teeth 207. This limit switch cuts the main power line so that the main motor is inoperative when the hand crank 205 is engaged. When the crank 205 has been engaged with the jack shaft, the crank is rotated in a direction to reverse the drum and the dies, unscrewing the partially formed balls from the machine for inspection.

If desired, an auxiliary feed may be employed for constantly urging the wire forward through the chuck 195. This auxiliary feed might consist of two power-driven serrated rollers in engagement with the wire and driven by a motor through a friction clutch.

In FIG. 14, the drum and gear both rotate in a counterclockwise direction. The idler gears 137, 137' and the die drive gears 138, 138 are all journaled in the drum and so rotate with the drum. If the gear 135 and the drum were to rotate at exactly the same speeds, there would then be no rotation of either the gears 138, 138, or of the dies; but after the drum has made one revolution, the dies must roll about the wire pitch diameter so that the wire has advanced on the circumference of the die pitch diameter. In order to do this, the gear 135 must rotate one and a fraction turns while the drum makes one turn. This is accomplished by proper selection of the ratio of the diameters of the pulley 121 on the jack shaft 120 and of the pulley 123 fixed to the drum, and of the ratio of the diameters of the pulley 131 on the jack shaft and of pulley 132 connected to gear 135.

The main drive motor 115 is mounted on a bracket 225 (FIG. 13) which is pivoted at 216 on the base or frame of the machine, and which is adjustable angularly about its pivot for belt take-up by a screw 218 that threads into the lug 219 at one side of the base 225. A bolt 221, which passes through an arcuate slot 222 at one side of the base 225, serves to adjust the belt take-up.

The rotating drum 112 may be made in three parts 112a, 11% and 1120 (FIG. 12). The parts 112a and 1121) are separated for ease in machining and may be made of high tensile cast iron, while the part 1120 should preferably be made of steel. These parts are to be machined all over so that the unit can easily be balanced for high speed rotation.

The die brackets similarly may be made in two parts so that the die can be assembled. The two parts are tongued and doweled in place. Screws secure the two parts together. The brackets are tongued into the drum and secured to the drum by studs 230 (FIG. 12).

The dies may vary in diameter, but both dies are ground to exactly the same diameter. With the die brackets removed from the machine, a new die may be mounted in a bracket and the bracket replaced in the machine.

To match different ball sizes and consequently different pitches between balls, the rate of travel of the end guide 175 must be set to match. This is done by adjusting the T bolt 166 in the slot 167 which alters the proportions of the lever 168. For ease in making the adjustment a scale may be attached to the lever 168.

A discharge duct is provided for removal of the completed balls from the machine. To separate the necks from the balls a series of slots large enough to cause the necks to drop through, but not the balls, can be provided to collect these necks in a tray while the balls continue to the end of the discharge duct and fall into a larger tray. A lightly loaded finger within the discharge duct could actuate a counter to indicate to the operator the time for changing the dies.

Since a ball must pass the finger every fraction of a second, the failure of a ball to regularly operate the finger could be used to actuate a time relay to break the circuit to the main motor causing the machine to stop. This stoppage could be caused by the end of the wire having rolled off the last ball, or by a jam-up in the machine itself.

When the operator presses the start button to start the machine with a new wire, then, he must hold his finger on the start button until the first balls have operated the trigger finger located in the discharge duct which causes the relay to be locked in.

From the preceding description, it will be seen that in actual operation, when the drum is rotating, carrying the two rotating dies, and the wire is being fed between and by the dies, the balance of forces will prevent any tendency to rotate the wire. Furthermore, this balance of forces causes the wire to maintain a central position between the dies.

The working edges of the dies force the metal in and outward to fill the circular areas in the dies. Because of the progressive variation in height of the thread convolutions, the radial feed is built into the dies and can be varied to produce the best balanced conditions from one end of the other. The axial feed of the wire is produced by the lead of the circular die grooves.

While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall Within the scope of the invention or the limits of the appended claims.

Having thus described the invention, what I claim is:

1. The method of blanking ball bearings which comprises engaging two die members, each of which has its active surfaces arranged in a helical thread about its axis and grooves of circular arcuate profile shape disposed between successive convolutions of the thread and also helically arranged about said axis, with an elongate rod at diametrally opposite sides of the longitudinal axis of the rod,

and rotating said die members on their respective axes in engagement with said rod while simultaneously rotating said die members about the axis of said rod.

2. The method claimed in claim 1, wherein the threads and grooves of both die members vary in height from one end to the other of the die members.

3. The method claimed in claim 2, wherein the top lands of the thread also vary in width from one end to the other of each die member.

4. The method claimed in claim 3, wherein the threads and grooves of each die member increase progressively in height from the end which first engages the rod to the leaving end of the die member, while the top lands of the thread of each die member increase progressively in width in the recited direction.

5. The method claimed in claim 2 wherein the threads and grooves of each die member increase progressively in height from the end which first engages the rod to the leaving end of the die member, while the top lands of the thread of each die member decrease progressively in width in the recited direction.

6. The method claimed in claim 5, wherein the grooves of each die member are of uniform pitch and lead.

7. The method claimed in claim 3, wherein the grooves of each die member are of varying lead from end to end and the rod has the same diameter as the ball blanks to be formed.

8. The method claimed in claim 5, wherein the thread of each die member is of progressively decreasing width in the recited direction and approaches a knife edge at said leaving end.

9. The method claimed in claim 8, wherein each die member has a beveled rolling edge at its leaving end, and

the beveled rolling edge of one die member is of larger diameter than the corresponding edge on the other die member.

10. The method claimed in claim 8 wherein one die member has a radius greater than the other die member.

gressively increasing in height and progressively varying in width from the end of the die member which first engages said rod to the leaving end thereof, and

each of said die members has a helical groove between its thread which is of circular arcuate profile shape in cross section, and

means for rotating said die members on their respective axes in engagement with the rod while holding the rod stationary, and

while simultaneously rotating said cradle about its axis.

12. A machine as claimed in claim 11, wherein the thread of each die member progressively decreases in width in the described direction.

13. A machine as claimed in claim 11, wherein the thread of each die member progressively increases in width in the described direction.

14. A machine as claimed in claim 12, wherein the thread of each die member approaches a knife edge at the leaving end of the thread,

an end guide member is reciprocably mounted on said base for movement toward and from the rod to center and hold the ball being rolled off the rod during final rolling of a ball from the rod, and

means is provided for moving said end guide member toward and from the rod.

15. A machine as claimed in claim 14, wherein a stationary stripper pin is mounted within said guide member to strip a ball from the guide member during the return movement thereof.

16. A machine as claimed in claim 11, wherein one die member has a radius greater than the other by an amount equal to half the feed of the work per revolution of the cradle.

17. A die for blanking balls comprising a helically threaded member having a groove between its thread convolutions which is of progressively varying arcuate profile shape.

18. A die member as claimed in claim 17, which is of varying lead.

19. A die member as claimed in claim 17 which is of uniform pitch and lead.

20. A die member as claimed in claim 17, wherein the thread is of progressively decreasing width and approaches a knife edge.

References Cited UNITED STATES PATENTS 672,664 4/ 1901 Bornenann 72-71 1,309,938 7/ 1919 Ellsworth 72-71 1,534,726 4/ 1925 Marcy 72-95 RICHARD J. HERBST, Primary Examiner US. Cl. X.R. 29-148.4; 72-78 

